Manufacture of hydrogen peroxide



United States Patent 4 Claims. (31. 23-407 This invention relates to an improved process for the manufacture of hydrogen peroxide.

In Canadian Patent No. 673,355 issued on Oct. 29, 1963, there is disclosed a process for the manufacture of hydrogen peroxide by the reduction of the dis-odium salt of an anthraquinone disulphonic acid with hydrogen sulphide and subsequent oxidation of the reduced product with oxygen. The resulting hydrogen peroxide is separated from the alkaline disodium anthraquinone disulfonate solution by precipitation as calcium peroxide by the addition of calcium hydroxide at room temperature. The calcium peroxide product is separated from the aqueous solution of anthraquinone disulphonic acid salt and is subsequently converted to hydrogen peroxide by known methods such as that described in US. Patent No. 2,695,217. However, the known methods of converting calcium peroxide to hydrogen peroxide yield a solution or slurry of the calcium salt containing hydrogen peroxide from which the hydrogen peroxide must be separated. The elimination of the separation process therefore would simplify the recovery of the hydrogen peroxide from the reaction mixture.

Likewise in the process for the production of hydrogen peroxide by the reaction of barium peroxide with an acid, the hydrogen peroxide product must be separated from the barium salt.

It is an object of this invention to provide an improved process for the manufacture of hydrogen peroxide wherein an alkaline earth metal peroxide product is efl'ficiently converted to hydrogen peroxide. Another object is to provide a liquid-liquid extraction process for the recovery of hydrogen peroxide from alkaline earth metal peroxides. Additional objects will appear hereinafter.

The improved process of this invention comprises contacting an aqueous slurry of an alkaline earth metal peroxide with a water insoluble organic acid dissolved in a water-immiscible solvent, whereby the metal peroxide reacts with the organic acid to form an aqueous solution of hydrogen peroxide and a metal salt of the organic acid which is soluble in the water-immiscible solvent, separating the aqueous solution from the water-immiscible solution, treating the water-immiscible solution of the metal salt of the organic acid with an aqueous solution of an inorganic acid, thereby regenerating the organic acid, and separating the metal in the form of a salt of the inorganic acid from the water-immiscible solvent, the regenerated solution of the organic acid being then employed for the extraction of further portions of the aqueous slurry of alkaline earth metal peroxide. It has been found that the alkaline earth metal salt of the inorganic acid is either soluble or dispersible in the aqueous phase and therefore can readily be separated from the water-immiscible solvent.

It is envisaged as a modification of the aforesaid process that the solution of the alkaline earth metal salt of the organic acid dissolved in a water-immiscible solvent be extracted with water to remove residual hydrogen peroxide carried over into the Water-immiscible solvent. The aqueous solution of hydrogen peroxide thus obtained may be added to the aqueous solution of hydrogen peroxide obtained by the primary separation.

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The organic acids suitable for employment in the process of this invention include those branched chain organic acids containing at least eight carbon atoms and which are substantially water-insoluble but are soluble in Water-immiscible solvents. It has been found that suitable organic acids are naphthenic acid, di(2-ethy1hexyl) phosphoric acid, Z-ethylhexanonic acid and tertiary monocarboxylic acids with nine to eleven carbon atoms in the main chain known as Versatic 911.

The water-immiscible solvents suitable for use in the process of invention are aromatic and aliphatic hydrocarbons which do not react with peroxide and which have serviceable viscosity and volatility at room temperature. Examples of said solvents are xylene, toluene, n-hexane, cyclohexane and kerosene.

Water soluble acids suitable for regeneration of the water-immiscible organic acid include sulphuric acid, sulphurous acid, phosphoric acid, hydrochloric acid and nitric acid. It has been found that carbon dioxide may be employed to regenerate 2-ethylhexanoic acid and tertiary monocarboxylic acids containing nine to eleven carbon atoms in the main chain. Regeneration with carbon dioxide has commercial attraction in the case of the latter carboxylic acid since a cyclic process is possible, the byproduct calcium carbonate being calcined to form dilute carbon dioxide (ca. 30%) which can be used again for conversion of additional portions of the calcium salt of the carboxylic acid.

The process of this invention may be carried out with any of the known apparatus which can be used for liquidiquid extraction. Equipment may be of the type used for continuous counter current extraction or may be mixingsettling tanks.

More particularly, in the preferred embodiment of this invention, the calcium peroxide slurry which normally contains small amounts of the sodium salt of an anthraquinone disulphonic acid is extracted with a solution of the organic acid (10% to 50% by weight) in a waterimmiscible solvent. The distribution coel'ficients of hydrogen peroxide and the organic acid calcium salt between the organic and aqueous phases are such that the majority of the hydrogen peroxide will remain in the aqueous phase and the organic salt will remain in the water-immiscible phase. The two phases are then separated. The hydrogen peroxide remaining in the organic phase can then be extracted with a water wash. The calcium salt of the organic acid dissolved in the Water-immiscible solvent is then treated with an aqueous soltuion of an inorganic acid such as phosphoric acid. In this manner the organic acid is regenerated and the calcium salt of the water soluble acid is formed. The distribution co efiicients between the organic and aqueous phases are such that the organic acid remains in the water-immiscible solvent. The calcium salt of the inorganic acid remains dissolved or dispersed in the aqueous phase. After separation of the two phases the organic acid can then be used for the treatment of the next portion of calcium peroxide.

In comparison to the usually employed processes for the recovery of hydrogen peroxide from calcium peroxide, the liquid-liquid extraction procedure of this invention provides a much higher concentration of hydrogen peroxide in aqueous solution. For example, using calcium peroxide octahydrate, aqueous solutions containing 15 to 17% hydrogen peroxide can be obtained. In normally employed processes, the concentration of hydrogen peroxide is likely to be less than 5%.

The invention is additionally illustrated by the following examples.

Examples I-14 A series of experiments was carried out wherein hydrogen peroxide was recovered from calcium peroxide employing solutions of 2-ethylhexanoic acid in Xylene. The said solutions contained Z-ethylhexanoic acid in concentrations in the range from to 33% by weight. The calcium peroxide was employed as calcium peroxide octa- 4 CaO /H O being 2/ l). The calcium peroxide was agitated at room temperature with the organic acid solution and the organic solution was then removed by decantation. The decanted organic solution was then extracted with hydrate, calcium peroxide dihydrate and an aqueous 5 water to remove dissolved hydrogen peroxide. The perslurry of anhydrous calcium peroxide (ratio of CaO /H O centage of hydrogen peroxide in both the aqueous solubeing 2/1). The calcium peroxide was agitated at room tions was then determined. The results of the experiments temperature with xylene/acid solution and the xylene are shown in Table 11.

TABLE 11 Percent Percent Percent Solvent, Feed-Solid Ratio H20; in 1110; 11202 Total Ex. percent tertiary component Solvent aqueous recovered recovered recovery,

monocarboxylic of aqueous to Feed phase in aqueous from organic percent acid phase phase phase 25%lr1xylene CaOz-8Hz0 100/10 14.8 75 24 90 d0 CaOg-8Hz0 1,000/100 14.8 79 15 94 do CaOg 1,000/33 21.2 47 22 e9 50% inxylene CaOrBHzO 100/20 15.3 75 15 00 19- ,do Geo, 100/7 27 e0 36 9e 20 %inkerosene.-- CaOz-8H1O 100/10 11.2 50 s 04 The percentages are by weight.

solution was then removed by decantation. The decanted xylene solution was then extracted with water to remove dissolved hydrogen peroxide. The percentage of hydrogen peroxide in both of the aqueous solutions was then determined. The results of the experiments are shown in Examples 21-25 A series of experiments was carried out wherein hydrogen peroxide was recovered from barium peroxide employing solutions (25% by weight in xylene) of ethyl- Table I. hexanoic acid, di-(2-ethylhexyl) phosphoric acid, naph- TABLE I Solvent, Percent Percent Percent Feed-Solid Ratio Percent H 0; 1110; Total Ex ethylcomponent Solvent H202 in recovered recovered recovery, hexanoie of aqueous to Feed aqueous in aqueous from Percent acid in phase phase phase organic xylene phase 1. 10 CaOz-SHzO 100/6 20.0 71.0 22 93 10 CaOz-ZHzO 100/3 74 10 CaOz 100/2 21.0 39 39 78 20 CaOz8H2O 100/11 15. 6 77. 7 10.3 94 20 CaOz-2HzO 100/4. 8 42. 8 47. 7 50. 8 08. 5 20 CaOi 710/% 24. 6 79 23 102 20 CaOz-ZHzO 925/65 30. 5 57 28 85 25 02102-81110 100/15 16. 7 80.1 21. 8 101. 9 25 CaOz-SHzO 100/15 17.1 87. 4 10. 4 103.8 25 CaOi-8I-IzO 300/ 14. 6 83 25 0:10; 1, 000/ 35.1 37. 4 51. 5 88. 9 25 CaOz 175/7. 5 27. 6 58. 3 20. 4 87. 7 25 C802 415/16. 5 28. 8 55. 5 32. 2 87. 5 33 05102-81120 100/20 16. 9 79. 1 21. 7 100. 8

The percentages are by weight.

It can be seen that if the organic phase is extracted with water after separation from the aqueous phase effective conversion of calcium peroxide to hydrogen peroxide is attained.

Examples 15-20 thenic acid and the tertiary monocarboxylic acids with chain lengths of nine to eleven carbon atoms (Versatic 911). The barium peroxide was employed either as a slurry in water equivalent to one quarter of the volume of the organic solution or was added to a two phase system of organic solution and one quarter its volume of water. The two phase system was agitated at room temperature and the organic phase separated by decantation. In Examples 21 to 24 additional water was added prior to decantation. In the case of Example 25 the organic phase was decanted and then extracted with an additional portion of water. The percentage of hydrogen peroxide in the aqueous phases was determined. The results are shown in Table III.

TABLE III Aqueous Phase Organic Phase, G. Solvent] Percent Total Ex Solvent System (Percent Acid in Xylene) Feed g. BaOz Percent Percent Recovery Recovery,

H2O; Recovery by Water- Percent by Decan- Extraction tation 25% ethylhexanoic acid B2101 slurrled in water /10 2. 89 84 25% di-(2-ethylhexyl) phosphoric acid BaOi (dry) 100/5 1.16 58 25% naphthenlc acid B302 slurried in water 100/7 1. 02 36. 5 25% tertiary monoearboxylic avid do 100/7 1. 98 71 71 25% tertiary monocarboxylic acid BaOz (dry) 100/6 8. 8 42. 5 30 72. 5

The percentages are by weight.

It was found that the organic solutions of the alkaline The eifectiveness of the regeneration procedure is shown earth metal salts of organic acids were readily regenerated in Table IV.

. TABLE.IV

Percent Calcium in Ratio Equiv. Organic Solvent Percent Example Organic Acid whose Calcium Salt is dissolved in Inorganic acid Acid/Equiv. Regenera- Organic Solvent Calcium tion Initial Final 26 Di(2-ethylhexyl) phosphoric Acid in Kerosene (35%). E01 (2N) l. 6 2. 47 0.002 99.9

27 Di-(2-e)thylhexyl) phosphoric Acid in Cyclohexane H2804 (0.61 N) 1.0 1.22 0.06 95 28 Dik-(2 yegthylhexyl) phosphoric Acid in Cyclohexane E2804 (1.0 N) 1. 6 1.22 0. 014 99 29..-- 2-ethylhexanoic acid in Xylene C02 gas* (100%) 1. 4 0.045 97 30 Te(rtiar)y monocarboxylic acidVersatic 911 mXylene O02 gas* (30% in nitrogen) 1. 36 0.036 97 31 Naph henic Acid in Oyclohexane (25%) so? gas (11%111 air) 0.88 0.005

*Gas was bubbled through the two-phase system.

by contacting with equivalent volumes of dilute (3 molar) 20 What we claim is:

solutions of either hydrochloric or nitric acids. The in- 1. A process for converting calcium peroxide or barium organic acids formed salts with the alkaline earth metals peroxide to hydrogen peroxide which comprises contacting regenerating the organic acids. The inorganic salts of alsaid peroxide in the presence of acid-free water with a kaline earth metals were readily extracted in the aqueous water-insoluble organic acid dissolved in a water-immissolution of inorganic acid. 25 cible solvent, thus forming an aqueous solution of hydrogen peroxide and a solution of the calcium or barium salt Examples 2641 of the organic acid dissolved in the water-immiscible sol- A series of experiments was carried out in which difiervent, separating the aqueous solution of hydrogen peroxide ent organic acids were regenerated from their calcium from the water-immiscible solution, contacting the Watersalts, the calcium salt being in solution in an organic immiscible solution of the calcium or barium salt of the solvent. organic acid with an aqueous solution of an inorganic In Examples 26-28 the solution of the calcium salt of acid, thus forming the calcium or barium salt of the inthe organic acid dissolved in the organic solvent was organic acid and a solution of the regenerated organic shaken with an aqueous solution of the inorganic acid, the acid in the water-immiscible solvent, and separating the equivalent ratio of acid to calcium being as indicated in said alkaline earth metal salt from the solution of the re- Table IV. The aqueous solution was then separated from generated organic acid.

the organic solution. The content of calcium in the or- 2. A process as claimed in claim 1 wherein the waterganic solution was determined before and after the reimmiscible solution of the calcium or barium salt of the generation step. organic acid is extracted with water to remove the hydro In Examples 29-31 the organic solution of the calcium gen peroxide dissolved the i salt of the organic acid was placed in a vessel with half 3. A process as claimed in claim 1 wherein the organic its volume of water and the gas (carbon dioxide or sulphur acid is a branched chain organic acid containing at least dioxide) was bubbled through the two phase system. In eight carbon atoms.

Example 30 the carbon dioxide was diluted with nitrogen. 4. A process as claimed in claim 1 wherein the organic In Example 31 the sulphur dioxide was diluted with air. acid is selected from the group consisting of di(2-ethyl- The two phases were then separated. The calcium content hexyl) phosphoric acid, naphthenic acid, 2-ethylhexanoic of the organic solvent was determined before and after acid and tertiary monocarboxylic acids with chains conthe regeneration step. taining nine to eleven carbon atoms.

References Cited UNITED STATES PATENTS 2,614,907 10/1952 Cook 23-207 OTHER REFERENCES Peppard et al.: Fractional Extraction of the Lanthanides as Their Di-Alkyl Orthophosphates, J. Inorg. & Nuclear Chem. 4, pp. 334-343 (1957). I OSCAR R. VERTIZ, Primary Examiner. H. S. MILLER, Assistant Examiner, 

1. A PROCESS FOR CONVERING CALCIUM PEROXIDE OR BARIUM PEROXIDE TO HYDROGEN PEROXIDE WHICH COMPRISES CONTACTING SAID PEROXIDE IN THE PRESENCE OF ACID-FREE WATER WITH A WATER-INSOLUBLE ORGANIC ACID DISSOLVED IN A WATER-IMMISCIBLE SOLVENT, THUS FORMING AN AQUEOUS SOLUTION OF HYDROGEN PEROXIDE AND A SOLUTION OF THE CALCIUM OR BARIUM SALT OF THE ORGANIC ACID DISSOLVED IN THE WATER-IMMISCIBLE SOLVENT, SEPARATING THE AQUEOUS SOLUTION OF HYDROGEN PEROXIDE FROM THE WATER-IMMISCIBLE SOLUTION, CONTACTING THE WATERIMMISCIBLE SOLUTION OF THE CALCIUM OR BARIUM SALT OF THE ORGANIC ACID WITH AN AQUEOUS SOLUTION OF AN INORGANIC ACID, THUS FORMING THE CALCIUM OR BARUM SALT OF THE INORGANIC ACID AND A SOLUTION OF THE REGENERATED ORGANIC ACID IN THE WATER-IMMISCIBLE SOLVENT, AND SEPARATING THE SAID ALKALINE EARTH METAL SALT FROM THE SOLTUION OF THE REGENERATED ORGANIC ACID. 